Date: Sun, 4 Nov 2007 17:41:34 +0100 From: Peter Schuller <peter.schuller@infidyne.com> To: freebsd-current@freebsd.org Subject: Re: ZFS Hangs Message-ID: <200711041741.43337.peter.schuller@infidyne.com> In-Reply-To: <472DBA71.9070401@FreeBSD.org> References: <200711021208.25913.Thomas.Sparrevohn@btinternet.com> <200711041302.08877.peter.schuller@infidyne.com> <472DBA71.9070401@FreeBSD.org>
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[-- Attachment #1 --] > Well the readahead "issues" are just the zfs design, AFAIK. It does > aggressive prefetching to improve performance on the assumption that you > are running with a reasonably fast storage system that can keep up. On > crappy low end disk hardware (e.g. single ATA disk) this can easily > saturate the disk. Well, regardless of the absolute performance you don't want the read-ahead to consume to much of the relative bandwidth/seek time available. Personally I didn't experience any prooven issues with prefetch; I disabled it on general recommendation back in the i386/1gb days and told myself I saw an improvement. I never looked into it carefully, other than that I previously had a general feeling that I saw a lot more I/O on the pool than what was read by applications. My memories are vague. -- / Peter Schuller PGP userID: 0xE9758B7D or 'Peter Schuller <peter.schuller@infidyne.com>' Key retrieval: Send an E-Mail to getpgpkey@scode.org E-Mail: peter.schuller@infidyne.com Web: http://www.scode.org [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.4 (FreeBSD) iD8DBQBHLfZHDNor2+l1i30RArC4AJ4yNkNuK9j0MgkPBsX31DxXt/O8qgCeN7pw r9u+2BVu5FPAKWIYsmvvl8o= =WQN5 -----END PGP SIGNATURE-----help
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